Replace modulo with compare-and-reset for circular buffer indices

Modulo generates a full division on ESP8266 since API_MAX_SEND_QUEUE
is not a power of 2. Use increment + compare instead.

esphome/components/api/api_overflow_buffer.cpp

@@ -31,7 +31,8 @@ ssize_t APIOverflowBuffer::try_drain(socket::Socket *socket) {
     // Entry fully sent — free it and advance
     Entry::destroy(front);
     this->queue_[this->head_] = nullptr;
-    this->head_ = (this->head_ + 1) % API_MAX_SEND_QUEUE;
+    if (++this->head_ >= API_MAX_SEND_QUEUE)
+      this->head_ = 0;
     this->count_--;
   }
 
@@ -62,7 +63,8 @@ bool APIOverflowBuffer::enqueue_iov(const struct iovec *iov, int iovcnt, uint16_
     }
   }
 
-  this->tail_ = (this->tail_ + 1) % API_MAX_SEND_QUEUE;
+  if (++this->tail_ >= API_MAX_SEND_QUEUE)
+    this->tail_ = 0;
   this->count_++;
   return true;
 }